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If someone claims they don't have a single bad habit, you can be pretty certain that individual is lying. And dishonesty, as a recent study shows, is its own bad habit.

Research from University College London and Duke University published in the journal Nature Neuroscience argues that little lies can lead an individual to telling larger ones.

The team, led by Neil Garrett, MSc, combined brain imaging with a test that allowed individuals repeated opportunities to act dishonestly. They had 55 people look at pictures of jars full of pennies, and asked them to tell a partner how much money was in the jar. Sometimes, researchers adjusted the incentives to reward people who lied—allowing them to pocket the difference between what they said and what their partner said, for example.

Using functional MRI, the team looked to see if continued dishonesty over time would lead to changes in the amygdala. They discovered the brain's response to dishonesty decreased over time. Not only that, the size of such self-serving lies grew with repetition.

"Taken together, our results reveal a biological mechanism that underlies the escalation of dishonesty, providing new insight into this integral part of human behavior," the authors wrote. "The results show the possible dangers of regular engagement in small acts of dishonesty, perils that are frequently observed in domains ranging from business to politics and law enforcement."

Researchers called for further work to investigate if people grow to accept violent acts or risky behaviors, though it appears lying can become a habit.

"Despite being small at the outset, engagement in dishonest acts may trigger a process that leads to larger acts of dishonesty further down the line," Garret et al. wrote.